A massive development of mucilage and a case of partial mortality in the Mediterranean gorgonian Paramuricea clavata is reported. Mucilage affected the benthic biocoenosis and particularly a gorgonian population on a shoal off the small town of Scilla (Regio Calabria, southern Italy) at the end of summer 1993. A mass of Ionian water rich in nutrients was probably isolated along the Calabrian coast in summer 1993. The meteorological conditions in August and September led to the warming of the water mass, and induced a bloom in mucilage producers. Smothing due to macroflakes entangled in gorgonian branches for several weeks caused the progressice necrosis of the underlying coenenchymal tissue. The entire population was affected by tissue necrosis: about 5 000 colonies, living in the 29 to 39 m depth range, underwent severe degeneration.